1999 Subaru Legacy Timing problem?

We just purchased a 1999 Subaru Legcay with 95000 miles for my wife. We took it to Subaru for their "24 point inspection" and they claimed everything looked good but recommned the 90000 mile tune up which includes a timing belt change along with fluid and filter changes. Their price seemed high, so after calling around we took it to a local mechanic who changed the timing belt and water pump (it was recommended to change the water pump while doing the timing belt given the mileage, eveen though it wasnt showing any problem), they also found an oil like at the crank seal and fixed that. I have changed the transmission fluid and filter and fuel filter. The problem now is that (about a week after getting it back from the shop) is that the engine will start up without issue but then immediately shut off in 5-10 seconds, even while gving it gas. I put the original fuel filter on to see if that was the culprit but the problem persisted. Could the timing belt replacement have been botched to create this problem? An additional note, while trying to start it for the 3rd or 4th time in a row I noticed a quick, small spark come from the passengar side of the engine and a faint odor. I took the spark plug wires off on that side and and didn't see or smell anything coming from them. The engine is a dual overhead cam and I have been told that the problem sounds almost electrical and could be the timing sensors that might be on each side. Any help or info would be greatly appreciated so that I know what tone to approach the mechanic with tomorrow.